Phylogeny of Arthropods Arthropoda Worm-like Ancestor Trilobites (extinct) Annelids (worms) Onychophorans (worms w/legs) Chelicerates (spiders) Crustaceans (lobsters) Insects (butterflies)

General Characteristics metamerism (segmented body) jointed appendages bilateral symmetry secreted exoskeleton ecdysis (molting) open circulatory system ventral nerve cord and brain

DIVERSITY Numbers about 80% of all animals are arthropods estimated to be over 30 million arthropods far more of them than all other metazoan species combined in virtually every conceivable environment: marine, terrestrial, freshwater, and aerial habitats. Phylum Arthropoda Subphylum Trilobita (extinct) Subphylum Chelicerata Subphylum Crustacea Subphylum Uniramia (insects)

Phylum Arthropoda Subphylum Trilobita (extinct) Subphylum Chelicerata Subphylum Crustacea Subphylum Uniramia (insects)

NERVOUS SYSTEM

Open Circulatory System Doral heart surrounded by pericardial sinus Blood (hemolymph) enters heart through ostia (openings) pumped through arteries Hemolymph- colorless; contains hemocyanin Hemocoel- blood cavity

Open Circulatory System

Compound Eye Facet Lens Crystalline cone Pigment cells Visual cells Nerve fibers from visual cells Optic nerve Ommatidia

1. General most arthropods are gonochoric fertilization may be external or internal in aquatic arthropods always internal in terrestrial species 2. Sperm Transfer sperm transfer usually by mating or copulation females usually store the sperm in a seminal receptacle REPRODUCTION

Subphylum Trilobita mya Earliest arthropod

Trilobite eye

Subphylum Chelicerata xiphosurans (horseshoe crabs), arachnids, sea spiders mostly terrestrial cephalothorax-abdomen 6 pairs cephalothoracic appendages chelicerae, pedipalps, 4 pairs legs no antennae

a. Xiphosura (horseshoe crab, Limulus polyphemus) b. Arachnida most chelicerates are arachnids several taxa (orders), many are common and familiar SCORPIONES (scorpions ) ARANAE (spiders ) OPILIONES (harvestmen, daddy longlegs ) PSEUDOSCORPIONES (pseudoscorpions) ACARINI (mites and ticks ) c. Pycnogonida (the giant sea spider, Colossendeis australis) Subphylum Chelicerata

Limulus is a benthic scavenger and predator. Prey include clams and other invertebrates that it digs for in the sand. The tail spine is used as a self-righting mechanism if the animal is overturned accidentally. Lives up to 19 years Reaches sexual maturity at about 9 to 12 years old Horseshoe Crab Limulus polyphemus, Carcinoscorpius rotunda, and Tachypleus gigas.

Mates during spring and summer full and new moons, onto ocean beaches. Females lay up to 30 thousand eggs, which males fertilize before burying them in the sand Horseshoe Crab

Arachnid

a heterogeneous taxon with many subtaxa two pairs antennae marine, freshwater, and terrestrial Primarily aquatic Free-floating larval stage 26,000+ known species Subphylum Crustacea

ANOSTRACA fairy shrimp and brine shrimp PHYLLOPODA tadpole shrimps, ostracod, water fleas MALACOSTRACA the largest, most heterogeneous, and diverse crustacean taxon shrimps, crabs, lobsters, mantis shrimps, pillbugs, crayfishes COPEPODA copepods enormous ecological importance as planktonic herbivores CIRRIPEDIA barnacles Subphylum Crustacea

Arthropod Development Zoea MegalopsNauplius

Gills a. General gills are evaginations typical of aquatic animals blood is oxygenated by gills oxygen delivered to tissues by blood b. Crustacean Gills crustacean gills are usually associated with appendages blood circulates through the gill and is oxygenated c. Book Lungs present in many arachnid orders similar to book gills of horseshoe crabs oxygen transport from the lungs to the tissues is by blood Respiration

Subphylum Uniramia

Decorator Crab Sponge crab Camouflage

Camouflage: anemone crab

coral guard crabs and pocilloporid corals

gall crabs and pocilloporid corals

scarlet cleaner shrimp

sea cucumber crab and sea cucumbers

pompom crabs and sea anemones